


Anything You Ask

by yensidlove



Category: Undertale (Video Game)
Genre: Alternate Universe - Underfell, M/M, Sensitive bones, Sibling Incest, Soul Sex, Underfell Papyrus, Underfell Sans
Language: English
Status: In-Progress
Published: 2016-03-02
Updated: 2016-03-02
Packaged: 2018-05-24 06:11:22
Rating: Mature
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,654
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/6144096
Author URL: https://archiveofourown.org/users/yensidlove/pseuds/yensidlove
Summary: <blockquote class="userstuff">
              <p>Sans will do just about anything Papyrus asks of him. When Papyrus truly realizes this, and the implications behind it, he makes a move.</p>
            </blockquote>





	Anything You Ask

**Author's Note:**

> i'm still going to hell!
> 
> how are you?

Sans and Papyrus were equally aware that the former had a funny disposition. Not in the ha-ha funny way; his jokes were never very good. They were terrible, really. No, this kind of funny was weird and probably concerning. Especially since it involved Papyrus so heavily.

As much as he protested, complained, and pretended against it... Sans had a soft spot for Papyrus.

Whatever Papyrus wanted, Sans did it. Usually with little to no regard for his well-being, which _should_ have upset the taller brother. After all, obedience was a sign of weakness and to be selfless was to be dead. He hated to see the shorter skeleton weak when he knew full-well that he was stronger than most monsters in existence. Even with 1 HP he was a force to be reckoned with.

And with 1 HP, he was even more of a target. Papyrus worried about that more than he liked to admit. He hated when he had to worry.

However, in this instance, Papyrus found that he enjoyed this flaw his brother had. It was useful to his advantage and as it was a flaw only exploitable by the tall skeleton he saw little reason to force Sans to change. Privately, Papyrus took pride in the fact that a monster as powerful as Sans felt he was worth listening to.

Although he had utter confidence in himself and trusted that if he made a show of force it would acquire the respect he deserved, it was... nice, to not have to. To just know inherently that his brother would do as he asked of him. Sometimes he still went with intimidation or violence around Sans, but it was more due his anger and impatience lashing out.

Papyrus undid his scarf, gaze unfocused as he stared at the TV. The familiar color bars were on again, indicating that there weren't any broadcasts available. He mulled over Sans' peculiar issues while he undid the clasps of his cape and pauldrons.

A few days back, before their morning patrol, he had told Sans to take off his disgusting shirt; there were mustard stains all around the neckline. Sans had done so easily enough, though he grumbled about how it wasn't _that_ dirty. He had yanked it off and thrown it at Papyrus who hadn't entirely expected the immediate reaction

He had caught the shirt just fine, but his cheekbones flared with color at Sans' exposed rib cage and spine. An absolutely lewd gesture as far as the tall skeleton was concerned. Papyrus, to his credit, had only growled and gone to the laundry basket. There was no need to let on that the little shit had flustered him. When he returned Sans had pulled on his favorite black jacket and zipped it up to hide his bones.

After they had parted ways on patrol, Papyrus spent his entire walk with his mind on those bones. Sans' bones. If he were to be honest, he hadn't stopped thinking about them since that morning. It was just so irritating and strange, so out of character.

For as long as he'd known Sans, his entire life, the skeleton never removed his shirt so openly. Which made sense, really. He had a certain... sensitivity to his ribs. The same sensitivity Papyrus had to his neck bones. Papyrus always felt oddly naked with his scarf off for that reason. He only ever had it off when on his own at home, after patrols and training were over, as he did now.

So, for Sans to have no qualms with being bare that way, it meant something. It meant he would willingly expose his weaknesses and insecurities. And all Papyrus had to do was ask. The idea of it sent a shiver down his spine. It had never truly dawned on him, the enormity of it; he really could make Sans do anything. That was a lot of power for one monster to wield.

The second-in-command of the royal guard frowned. He pulled off his gloves and looked at them, contemplative.

 _Speak of the devil and the devil appears._ Papyrus jolted, caught off-guard. The air in the living room did something that the young guard still couldn't begin to understand. The empty space just to the left of the couch breathed in and out, somehow, as if a suction or a void appeared and then disappeared in an instant. When it finished Papyrus blinked and Sans was suddenly there. All of his poor posture and casual style choices included.

"ah, home sweet home," Sans joked. Which was nothing new, except it didn't seem to be aimed at him. Papyrus raised a brow.

He also looked relaxed, which made Papyrus squint. Sans was never totally relaxed unless alone. Even in his sleep, in his own house, the older brother was on edge. So that meant...

Sure enough, as if to validate his assessment, Sans yawned and scratched his side before he made to ascend the stairs. Without even a glance in Papyrus' direction.

He hadn't noticed his presence. Papyrus smirked. Well, what a fantastic opportunity.

The slim skeleton set his gloves aside as quietly as he could and took two long strides to wind up directly behind Sans on the stairway. Still oblivious. Impressed with his own stealth abilities, Papyrus reached out a hand to grab his brothers shoulder.

Just in time, Sans tensed and spun around in a way that shouldn't have been possible. Sans always did things that were inexplicable. Papyrus made a triumphant noise, pleased he had surprised his brother, which turned into shocked gasp when Sans' weird displacement magic dislodged his grip and made him tip backwards.

Papyrus latched onto Sans' arms and dragged the short monster with him as he shouted and tumbled backwards down the stairs.

The two of them tangled together at the foot of the staircase. Sans groaned and Papyrus opened his mouth to yell at him but cut short when he spotted where he was.

Sans was atop Papyrus, but slightly higher up on him because of how they had fallen. And so Papyrus was face-to-ribs with his brother. His hoodie definitely wasn't zipped up anymore. Papyrus made an undignified noise and scrambled back to get away but only succeeded in putting his face level with Sans' face.

"SANS!" Papyrus shrieked, face lit with a reddish blush and teeth bared in anger. The last thing he wanted was to be confronted with his embarrassment where Sans could see.

"ugh, boss, can you not scream in my ear? holy fuck," Sans complained, unaware of his brothers minor breakdown. He rubbed his skull and sat up some, but not enough to let Papyrus up. The tall skeleton thrashed and backpedaled underneath him.

"SANS, YOU _IDIOT_ , GET OFF ME THIS INSTANT! YOU ARE INDECENT!!" Papyrus growled and huffed, eyes pointedly averted, but he didn't reach out to shove the shorter off. If he did, he'd have to touch Sans' exposed bones. His jacket was half-way down one shoulder now and Papyrus could see every part of his clavicles.

While Papyrus moved and hollered, Sans finally caught on. He looked from his own chest to Papyrus' red face and raised an eyebrow. Once what Papyrus said clicked, he rolled off his brother and sat back on the floor. His left eye socket, lit with the typical red glow, followed Papyrus' movements as he leapt to his feet.

"indecent, huh?" He parroted back, amused. Papyrus glared at his grin and crossed his arms, cheeks still tinted.

" _YES_ , Sans! Indecent. Your ribs are just... out there!"

Sans snorted and stretched out in his seated position on the ground. He lifted one side of his jacket and winked at Papyrus who spluttered, "whatsamatter, boss? are my ribs rattlin' ya?"

Papyrus stiffened and shouted in anger. He reflexively conjured a bone and chucked it at Sans who fell to one side in an easy dodge. Now laid on his side, the shorter skeleton brother yawned for show and shifted so his jacket was hardly on him anymore. Sans bounced his brows and chuckled when Papyrus fumed.

"SANS! You—" Papyrus paused and his eye sockets narrowed. Sans evidently really didn't mind to have himself exposed around Papyrus, as long as it was for a good reason. Which, apparently, included to tease him. That was interesting.

For a moment Papyrus just looked at Sans, who stared expectantly up at the younger skeleton. With his jacket almost off, he looked debauched, and prepared. Like he was ready for whatever could be thrown at him. Slowly, Papyrus smirked.

He'd just have to test that confidence.

"Sans," he restarted at a more reasonable volume. Sans grin fell in confusion. "Follow me," Papyrus crooked a finger at him and then walked past him up the stairs to his room. He went in and purposely left the door open.

As expected, only a few moments passed before Sans grunted softly and then followed him up to his room. He stood awkwardly in the doorway as red tinted sweat started to bead on his forehead. "alright so i'm here. where the fuck are ya goin' with this, boss?"

Papyrus looked over his shoulder at his brother, with his jacket only on one shoulder, and hummed in approval. "I'm going exactly here with this, Sans." He turned and crossed to the shorter skeleton so that he stood right in front of him. Sans grimaced as Papyrus towered over him.

With strengthened resolve and decisive movement, Papyrus reached out a hand to Sans. He ignored his brothers flinch, an understandable if pathetic reaction, and grabbed hold of his upper-most rib. Immediately, Sans sucked in a gasp and one of his hands flew up to grip Papyrus' wrist.

"b-boss, i—"

"You seem extremely keen to do what I ask of you, Sans," Papyrus chuckled, cheekbones red. He pushed through the lewdness of it to run his bony fingers along Sans' rib. "So. Does that make you as weak-willed as you are pathetic?" The shorter skeleton stuttered out a noise and looked up at Papyrus with spite and fear in his eyes. His grip on the taller' wrist bones tightened.

" _Or_ , does that make me just that much more excellent than anyone else?" Papyrus thumbed the underside of the rib bone experimentally and received a shudder in response. He felt it go all the way through Sans' short frame.

Sans' hand twitched and loosened on Papyrus. He laughed, bare and light like it was all he could get out. Then, he shook his head and made a vague gesture with his free hand. "definitely the uh, the second one there." Papyrus preened at the confirmation and placed his other hand on Sans' sternum.

"I knew it! Well, isn't that perfect... Now, about that little show you put on downstairs," Sans red eye disappeared momentarily and then shone back into existence when Papyrus hand broke free of his hold to trail down his ribs. Sans watched it warily.

"yeah, what of it?" Sans voice was low, petulant. His expression unreadable. Guarded. Papyrus rolled the bright red pupils that sat in his sockets and gripped the lowest of Sans' ribs. He gave the shorter a slight shake and growled in annoyance which made Sans sweat again.

"You stupid fucking idiot, I have my hands on your ribs and my cheeks are no doubt still red with my magic—" they were, "—If I hadn't _liked_ the show, do you really think I'd be standing here like this? Oh my god. You are an imbecile."

Papyrus reached under and into Sans' rib cage to run his palm along the underside of the ribs. He crouched some to reach in more. Below him, Sans quaked and made a strangled, pleased noise. Papyrus leaned back to appreciate the view, not surprised to find that wisps of red magic, brighter than his own, had gathered inside Sans chest just inches from where his fingers were.

"ah, b-boss, are you sure ya know what you—" Sans gasped mid-speech, taken aback when Papyrus' fingertip ghosted just a bit too close to where his soul had rapidly formed. His left eye flickered, expression blissful but then uncertain. He tried again. "i mean, you and me, we... we're—"

"I'm well aware of what we _are_ , Sans," Papyrus rolled his eyes as before, "Does it really look like that's stopping me? Fucking pay attention, would you?"

Sans' hackles raised, "i am paying attention, jackass, i just- nn, _shit_. i just wanted to make sure you're not making a mistake you're gonna regret later or some shit." Papyrus scoffed and stroked along the backside and front of Sans' sternum at the same time. Sans absolutely quivered under his ministrations.

"Really. When do I ever make mistakes, Sans?" Papyrus knelt all the way down to get a better look at the soul that had fully formed, proud and red with magic, behind Sans' ribs. The short skeleton chuckled, despite himself.

"what, you mean aside from all the times you mistook rocks for humans—?"

"Oh, shut the fuck up, Sans!" Papyrus poked harshly at his spine. Sans trembled, his chuckling broken and airy. He groaned and held onto Papyrus' upper arms to stay upright while his brother continued to feel him up from the inside out, undaunted.

"i was just look— ah, fuck!—lookin' out for you, ya fuck. jeez— _nngh!_ " Sans' legs shuddered as if to give out when Papyrus lent down to nuzzle at his clavicle. He ran his hands up higher to hold Papyrus' shoulders and paused, amazed at the lack of shoulder pads. Sans rubbed the bones there, just concealed under a layer of black fabric. His skull automatically slotted into the space where Papyrus' scarf usually was. He gave the neck bones there an experimental nudge with his mouth and chin.

Papyrus squawked and his body spasmed. Sans leaned back a bit, startled. The tall skeleton was stiff in his arms, but steady. When he noticed Papyrus hadn't pulled away, he went in again. Magic pooled in his mouth, behind his teeth, and a translucent red tongue folded out. He glanced up at his brother, who still hadn't made to get away, and then licked the same neck bones he had grazed before.

The reaction was immediate. Papyrus moaned and shifted some so that more of his neck was available. Sans chuckled and repeated the motion again, tongue smooth and wet against the ridges of the vertebrae.

Papyrus unraveled his arm from within Sans' chest and bent down a bit. He tucked both arms around his brothers middle and hoisted the shorter skeleton up and onto his bed just a few feet away. Sans wrapped his legs around Papyrus' hipbones and grinned lazily up at him.

"nice glow, bro," Sans nodded at Papyrus' chest which was exuding a rich, deep red color even through the dark tunic. The taller skeleton grunted in acknowledgement.

Papyrus hooked a few fingers onto Sans' upper ribs, and yanked him upward so their faces were just a hairs distance apart. Red unfurled from behind Papyrus' teeth, magic in the shape of a tongue. Sans swallowed on nothing and stared at it.

Papyrus pressed his teeth to Sans' and their bones clacked together. His tongue glided over his brothers and Sans moaned into the kiss. His legs tightened reflexively around Papyrus who bent him back to lay down on the bed.

Fingers still curled around bone, he stroked the ribs much to Sans' enjoyment. After Sans moaned a handful of times into his mouth, Papyrus broke the kiss and lent down to the side of Sans' skull, "So, you'd do _anything_ I told you to, hm?"

Sans grunted, "if you keep rubbing my ribs like that i sure fuckin' will, yeah."

"Good," Papyrus smirked and Sans visibly fought to restrain his reaction to the praise matched with that look, "Then I have some things I want to try."

**Author's Note:**

> idk if i'll continue this? but it's definitely an option. lemme know what you think!


End file.
